A chronicle of the decade-long hunt for al-Qaeda terrorist leader Osama bin Laden after the September 2001 attacks, and his death at the hands of the Navy S.E.A.L. Team 6 in May 2011.

Zero Dark Thirty opens with the sound of real 9/11 recordings, between victims and emergency services, played over a plain black background. We’re faced with echoes of the dying head-on, nowhere for us to hide. It’s harrowing, but this isn’t manipulation. The genuine screams of terror aren’t placed front and centre of Zero Dark Thirty to justify the investigation that comes after – it’s just fact, director Kathryn Bigelow is saying. This is just what happened, and the remainder of the film presents itself that way, torture and all.

About those controversial torture scenes – they’re grisly, yes, and Bigelow and her writer Mark Boal make no comment one way or another about the effectiveness of ‘enhanced interrogation’. The film is unbiased throughout, non-judgemental towards either terrorist or American spook. It is, rather, a journalistic document come to life, objective in its stance and precise in its eye for detail and accuracy to the point where everything feels like non-negotiable fact.

Controversy aside, and minus knowledge of the real-world context, a viewer wouldn’t question what Bigelow and Boal are saying. Boal’s journalism background lends itself to the script and gives us a riveting, straightforward account of the manhunt for Osama bin Laden. This is like a feature interpretation of a newspaper article – the ‘who what where why’ is what matters, and nothing more.

Bigelow’s own documentarian approach is cinema verite filtered through rapid Hollywood storytelling, with the director’s economy and singular focus almost Bresson-esque. Zero Dark Thirty takes a microscope to the minutiae of the bin Laden operation rather than taking much in the way of a look at the human impact. Character development is scant (though the cast all give distinct personalities to their characters, even though the film doesn’t really require them to do so), but the movie isn’t cold.

Zero Dark Thirty is too vibrant in style, too rich thematically to be accused of coldness. There are copious thrills – tailing a suspect through a crowded marketplace here, an assassination attempt on Jessica Chastain’s Maya there – but they have an urgency where even Bigelow’s nail-biting previous feature, the Oscar-winning The Hurt Locker, didn’t. The real-world angle adds a layer of unbearable tension.

That these events are based on truth adds not just further intrigue to Zero Dark Thirty’s thrills, but to its ethics as well. Much controversy arose around the film because it wasn’t accusatory enough for liberals, nor gung-ho enough for patriots. Zero Dark Thirty is a moral film precisely because it takes no sides in the debate, instead asking the audience to form its own opinions, to make its own arguments. Interpretations will differ, but it’s a rare film that encourages the viewer to assemble the film’s message themselves.

As the second-best ensemble of the year (Spielberg’s Lincoln still holds that prize), Zero Dark Thirty is a character actor extraordinaire, Jennifer Ehle, Mark Strong, Chris Pratt and Joel Edgerton all giving short but well-defined turns. As the lead, Chastain is solid, a welcome addition to Hollywood’s regrettably small gallery of strong women, but a brutish Jason Clarke is the standout here, playing a wily government agent with such confidence that he must know this is his breakout role. He’s followed closely by the effortlessly charismatic Edgar Ramirez, whose screen power alone lifts one of the most underwritten characters, a field operative that responds to being challenged by Pakistani locals with a cold “If they don’t move, shoot ‘em.”

Ostensibly a thriller, Zero Dark Thirty at times approaches horror. Not just in those waterboarding scenes, which take place within dark, windowless cells, but elsewhere; Pakistani police circling a terrorist suspect disguised in burkas; a horribly intimate and prolonged car bombing within friendly territory; that final, inevitable assault on the bin Laden compound of course, American soldiers storming the shadowy fortress by the dark of night.

There’s also a curious science fiction element to the picture, much of it taking place in an anonymous no-man’s land of otherworldly deserts and exotic townships. Aided by the eerie Alexandre Desplat score, Bigelow makes this world alien to us viewers. The director does not ease us in; our introduction to Chastain’s Maya and Clarke’s Dan takes place at an undisclosed ‘black site’, where a suspect – an enemy so unknowable that he may as well be an extraterrestrial – is being questioned while strung up to the ceiling. Bigelow throws us in at the deep end, refusing to dumb down or halt for a moment so we can adapt to our surroundings.

If there’s a criticism to be levelled at Zero Dark Thirty, it’s perhaps that adherence to the facts means the excellent, climactic compound raid, a 30-minute, almost real-time recreation of the assault, feels separate from the rest of the film. Zero Dark Thirty is, for the most part, a Zodiac-like exploration of obsession, focused on two people: Maya and Dan. When the narrative shifts from whip-speed, decade-spanning investigation by these driven individuals, to the final operation carried out in an extended scene by a just-introduced Navy Seal team, it feels like a move into another film.

You could take issue with the way Zero Dark Thirty presents itself, as a factually-sound study of the hunt for bin Laden. That would require intense research, and wading through the swamp of contradictory accounts regarding the whole affair until you find something approaching the truth. But, forgetting context and taken on its own terms as a piece of cinema, Zero Dark Thirty is a masterpiece. It’s the finest movie yet about 9/11 or its fallout and Bigelow’s best film to date, a stylistic companion to and progression from the already impressive The Hurt Locker. This will be very tough to follow.

Brogan Morris – Lover of film, writer of words, pretentious beyond belief. Thinks Scorsese and Kubrick are the kings of cinema, but PT Anderson and David Fincher are the young princes. Follow Brogan on Twitter if you can take shameless self-promotion.